Combine vinegar, water, and salt in a large saucepan and bring to a boil. While the brine heats, prepare 4 pint canning jars. Wash and trim the beans so that they're about 1/2-inch shorter than the jars. Divide the dill seed and garlic among the prepared jars. Pack the beans in the jars, leaving 1/2-inch clearance between the tops of the beans and the rim of the jar. Use a flat plastic spatula to press the beans away from the sides of the jar to fit all the beans in the jars.
Slowly pour the hot brine over the beans, again leaving 1/2-inch headspace. Discard any extra brine.
Wipe the rims to remove any spices or droplets of brine, apply the lids and rings and process in a boiling water canner for 10 minutes. When time is up, remove jars from the canner and let them cool on a folded kitchen towel or wire rack. Let these pickles cure for at least 2 weeks before eating.
